Here are the short answers for the important 2-mark and 3-mark questions based on the +2 Tamil Nadu State Board Physics syllabus:

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Lesson 1: Electrostatics

1. Define Coulomb's Law:
   Coulomb’s law states that the electrostatic force between two point charges is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them.
   Formula: $F = \frac{1}{4\pi\epsilon_0} \frac{q_1 q_2}{r^2}$

2. Electric Dipole:
   An electric dipole consists of two equal and opposite charges separated by a small distance.
   Dipole Moment (p): $p = q \times d$

3. Corona Discharge (Action of Point):
   It is the ionization of air near a sharp conductor due to high electric field, leading to discharge.

4. Applications of Capacitors:

   • Energy storage in circuits
   • Smoothing in rectifiers
   • Tuning circuits in radios and TVs

5. Properties of Electric Field Lines:

   • Field lines start from positive charge and end at negative charge.
   • They never intersect.
   • The density of lines indicates field strength.

6. Difference Between Coulomb Force and Gravitational Force:

   Feature	Coulomb Force	Gravitational Force
   Nature	Attractive or Repulsive	Only Attractive
   Strength	Stronger	Weaker
   Depends on	Charge	Mass

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Lesson 2: Current Electricity

1. Difference Between Drift Velocity and Mobility:

   Feature	Drift Velocity	Mobility
   Definition	Velocity of charge carriers due to applied field	Ability of charge carriers to move under an electric field
   Formula	$v_d = \frac{I}{nAe}$	$\mu = \frac{v_d}{E}$

2. Applications of Seebeck Effect:

   • Thermocouples
   • Thermoelectric generators
   • Temperature sensors

3. Kirchhoff's Laws:

   • First Law (Junction Rule): Sum of currents entering a junction equals sum of currents leaving it.
   • Second Law (Loop Rule): In a closed loop, sum of emf is equal to the sum of potential drops.

4. Joule’s Law:
   The heat produced in a conductor is directly proportional to the square of current, resistance, and time.
   Formula: $H = I^2 R t$

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Lesson 5: Electromagnetic Waves

1. What are Fraunhofer Lines?
   Dark lines in the solar spectrum due to absorption by elements in the sun’s atmosphere.

2. Applications of Infrared:

   • Night vision devices
   • Remote controls
   • Thermal imaging

3. Applications of Microwaves:

   • Satellite communication
   • Microwave ovens
   • Radar

4. Applications of UV Rays:

   • Sterilization
   • Detecting fake currency
   • Fluorescent lamps

5. Properties of Electromagnetic Waves:

   • Transverse waves
   • Travel at speed of light in vacuum
   • Do not require a medium

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Lesson 6: Ray Optics

1. Why Sky Appears Blue?
   Due to Rayleigh scattering, shorter blue wavelengths scatter more than longer red wavelengths.

2. Power of Lens:
   The ability of a lens to converge or diverge light.
   Formula: $P = \frac{1}{f}$ (in diopters)

3. Rayleigh’s Scattering:
   Scattering of light by particles smaller than its wavelength, explaining why the sky is blue.

4. Why Sky Appears Red in Morning and Evening?
   Longer red wavelengths scatter less than blue, allowing red light to dominate at sunrise and sunset.

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Lesson 7: Wave Optics

1. What Are Coherent Sources?
   Two sources having constant phase difference and same frequency.

2. What is Double Refraction?
   Splitting of light into two refracted rays in an anisotropic material.

3. Uses of Polaroids:

   • Reducing glare in sunglasses
   • 3D movie glasses
   • LCD screens

4. State Brewster’s Law:
   When light is incident at Brewster’s angle, the reflected ray is completely polarized.
   Formula: $\tan \theta_B = \frac{n_2}{n_1}$

5. Difference Between Fresnel and Fraunhofer Diffraction:

   Feature	Fresnel	Fraunhofer
   Source & Screen	Finite distance	Infinite distance
   Wavefront	Spherical	Plane
   Pattern	Changes with distance	Stable

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Lesson 8: Dual Nature of Radiation

1. Stopping Potential:
   Minimum potential required to stop photoelectrons.

2. Threshold Frequency:
   Minimum frequency required for photoemission.

3. Applications of Photoelectric Cell:

   • Automatic doors
   • Light meters
   • Solar panels

4. Applications of X-Rays:

   • Medical imaging
   • Security scanning
   • Crystallography

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Lesson 9: Nuclear Physics

1. Define Curie:
   One Curie = $3.7 \times 10^{10}$ disintegrations per second.

2. Half-Life Period:
   Time taken for half of a radioactive substance to decay.

3. Mean Life:
   Average lifetime of a radioactive atom.

4. What is Carbon Dating?
   Determining the age of ancient objects using C-14 decay.

5. Properties of Neutrino:

   • Zero charge
   • Very small mass
   • Penetrates matter easily

6. Properties of Neutron:

   • Neutral charge
   • Mass slightly greater than proton
   • Used in nuclear fission

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Lesson 10: Communication Systems

1. Define Skip Distance:
   Minimum distance from a transmitter where a skywave returns to Earth.

2. Define Skip Zone:
   Region between groundwave and skywave reception where no signal is received.

3. Applications of Zener Diode:

   • Voltage regulation
   • Overvoltage protection

4. Applications of LED:

   • Indicator lights
   • Display screens

5. Applications of Photodiode:

   • Optical communication
   • Light sensors

6. Applications of Radar:

   • Weather monitoring
   • Military surveillance

7. Applications of Satellite:

   • GPS
   • TV broadcasting

8. Merits & Demerits of Optical Fiber Communication:
   ✅ High speed, no interference
   ❌ Expensive, fragile

9. Advantages & Disadvantages of AM and FM Transmission:

   Feature	AM	FM
   Bandwidth	Low	High
   Sound Quality	Poor	Better
   Interference	High	Low

10. Applications of Solar Cell:

• Power generation in satellites
• Solar calculators

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